What is Metastases to the Liver

Liver metastases occur in the tissue of the liver, usually close to blood vessels. The liver has the second richest blood supply of the body, and therefore provides a very suitable environment for the growth of cancer cells.
The primary cancer site may be anywhere in the body, the most common sites are listed in “Predisposing Factors”.

Statistics on Metastases to the Liver

The liver is the second most common site of metastasis (spread of cancer), after the lymph nodes. Liver metastases have been found in 30-70% of patients who are dying of cancer. In the Western world, metastasis to the liver is more common than primary liver cancer. Liver metastases are most commonly seen in patients aged 50-70.

Risk Factors for Metastases to the Liver

Most cancers can metastasise to the liver. The following are those most likely to cause liver metastases:
 

  • Eye
  • Colon
  • Stomach
  • Pancreas
  • Breast
  • LungBrain tumours are virtually the only primary cancer that do not metastasise to the liver.Cancer commonly spreads to the liver because it provides a suitable environment for the growth of tumour cells. Gaps in the lining of liver blood vessels allow tumour cells to get close to the functional cells of the liver (hepatocytes). The liver also has a rich blood supply, supplying tumour cells with the nutrients and oxygen they require to grow.

    Progression of Metastases to the Liver

    Liver metastases are foreign tissue growing within the liver. They either grow expansively (as a mass) or infiltratively (spreading through surrounding tissues). Physically, they grow and compress the surrounding liver tissue. A connective tissue rim is usually formed around the metastasis, and surrounding tissue is wasted away. Large metastases may even compress branches of the portal vein. Because they grow so quickly, liver metastases, like primary tumours, may outgrow their blood supply, resulting in death of the centre of the lesion.
    Some specific cancer metastases have unique effects. Metastases from pancreatic and breast cancers result in fibrous scar formation. Some metastases throw off blood clots that may occlude the portal or hepatic veins. Others may cause areas of calcification that are readily detectable using radiographic imaging.
    Metastases rarely cause death due to pure metastatic burden. Compression of the vena cava (hindering blood return to the heart), blockage of drainage outflows (resulting in lung infection, for example), and electrolyte imbalance caused by abnormal hormone secretion are some causes of death.

    How is Metastases to the Liver Diagnosed?

    Liver function tests are not generally useful in the diagnosis of liver metastases, as changes do not appear until late in the course of the disease and even then may be non-specific.
    A full blood picutre (FBP) may reveal anaemia, increased numbers of white blood cells and slightly increased bilirubin levels.

    Prognosis of Metastases to the Liver

    Without treatment, patients who develop liver metastases live an average of 8.7 months.
    Prognostic factors include:
     

  • success of any surgical removal that may have been performed.
  • cancerous state of lymph nodes surrounding the portal veins.
  • extent of disease outside the liver.
  • number of metastases.
  • stage of primary cancer.

    How is Metastases to the Liver Treated?

    Because there are often multiple foci of disease, liver metastases are difficult to treat with surgery or even radiotherapy.
    Chemotherapy may be useful in a minority of cases.
    There are six “minimally invasive techniques” that may be curative or life-lengthening in some patients, including many colon cancer patients. These include:
     

  • Placement of chemotherapy agents directly into hepatic arteries, along with an agent to promote their slow release.
  • Freezing the tumours.
  • Use of microwaves to overheat and kill the tumours.
  • Direct injection of ethanol (alcohol) to kill the tumours.
  • Use of radiofrequencies to overheat and kill the tumours ().
  • Use of laser technology to overheat and kill the tumours.Treatment of metastatic cancer is generally palliative.

    Metastases to the Liver References

    1. Groenwald, S. Liver Cancer: Prognostic Factors 2000. CancerSourceRN http://www.cancersourcern.com/search/getcontent.cfm?DiseaseID=19&Contentid=17177 accessed on 21/3/05 at 4:40pm
    2. Harrison’s Online – Tumors of the Liver and Biliary Tract http://www3.accessmedicine.com.ezproxy.library.uwa.edu.au/content.aspx?aID=62808 accessed on 5/4/05 at 11:00am
    3. Nawaz Khan, A., Macdonald, S. Liver, Metastases 2003. eMedicine http://www.emedicine.com/radio/topic394.htm accessed on 21/3/05 at 1:20pm